Exhaust gas recirculation control for internal combustion engines

ABSTRACT

An exhaust gas recirculation (EGR) control arrangement for internal combustion engines incorporating vacuum relief means for dumping an output EGR signal, which ordinarily maintains an EGR valve in an &#39;&#39;&#39;&#39;open&#39;&#39;&#39;&#39; condition, whenever a venturi control signal achieves a predetermined relationship to the value of engine manifold vacuum, thereby causing the EGR valve to close.

United States Patent [191 Dawson et al.

[ 1 June 25, 1974 EXHAUST GAS RECIRCULATION CONTROL FOR INTERNAL COMBUSTION ENGINES [75] Inventors: Gary D. Dawson, Rochester; Robert S. Harris, Washington, both of Mich.

[73] Assignee: Chrysler Corporation, Highland Park, Mich.

[22] Filed: Aug. 2, 1972 [21] Appl. No.: 277,219

[52] US. Cl 123/119 A [51] Int. Cl. .l F02m 25/06 [58] Field of Search 123/119 A [5 6] References Cited.

UNITED STATES PATENTS Caldwell 123/119 A Primary Examiner-Wendell E. Burns Attorney, Agent, or Firm-Talburtt & Baldwin [5 7] I ABSTRACT An exhaust gas recirculation (EGR) control arrangement for internal combustion engines incorporating vacuum relief means for dumping an output EGR signal, which ordinarily maintains an EGR valve in an open condition, whenever a venturi control signal achieves a predetermined relationship to the value of engine manifold vacuum, thereby causing the EGR valve to close.- 7

8 Claims, 2 Drawing Figures I i I 1 EXHAUST GAS RECIRCULATION CONTROL FOR INTERNAL COMBUSTION ENGINES BACKGROUND This invention is concerned with systems and apparatus for controlling exhaust gas recirculation (EGR), particularly as applied to motor vehicles driven by internal combustion engines. The recirculation of portions of internal combustion engine exhaust back to the engine combustion chambers is coming into general use for suppressing to some extent the formation of NO, in the engine exhaust, the idea being to introduce inert substances, i.e., combusted exhaust gas into the combustion chamber in order to lower peak combustion temperatures therein, thereby reducing NO formation. An EGR valve is used to control recirculation of the exhaust gas. The valve is typically a vacuum operated valve.

SUMMARY This invention isparticularly directed to amplifier" EGR systems, as opposed to ported EGR systems. Amplifier systems are distinguished from ported systems in that the former utilize a vacuum amplifier controlled by venturi vacuum for providing controlled modulated vacuum to an EGR valve. In the ported systems the vacuum to the EGR valve is modulated by the throttle bladeat a port in the engine carburetor bore. Amplifier EGR systems have heretofore tended to have limited capability for controlling NO emissions. Specifically, manifold vacuum tends to vary widely depending on engine operation thus effecting the control of the EGR valve.

Some improvement in vehicle driveability has been obtained by using an amplifier arrangement wherein an input venturi vacuum is transformed into a vacuum of similar but stronger characteristics. For further improvement, it is suggested that a vacuum reservoir with check valve be provided in the manifold vacuum line to the amplifier to stabilize the source vacuum. However, this does not completely solve the" problems of this system. At conditions of wide open throttle (WOT) when full power is required from the engine, amplifier EGR systems with vacuum reservoir capability provide maximum exhaust gas recirculation thus depriving the engine of the capability of developing full power due to the excessive presence of inerts in the combustion chambers which such operation entails.

It is an object of this invention to provide an amplifier EGR system and apparatus in which means are incorporated for venting or dumping the reservoir vacuum or source vacuum. That is, the vacuum of the vacuum reservoir is dumped into the manifold vacuum thus preventing the application of an output vacuum to the EGR valve at WOT thereby closing the valve at WOT. Since this intentional disablement is controlled by venturi vacuum, specifically when it substantially approaches or exceeds manifold vacuum, it thereby occurs only under conditions of near or at wide open throttle when maximum power is required from the engme.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 represents a schematic diagram of an apparatus and system incorporating the vacuum relief feature of the invention;

FIG. 2.is across section ofan EGR vacuum amplifier designed to integrate the functions of vacuum reservoir, dump valve and amplifier in one unit thus greatly simplifying the plumbing required with the use of this invention.

DESCRII'T ION OF THE PREFERRED EMBODIMENTS The invention can best be understood by referring to the schematic of FIG. 1 which shows an improved EGR control system andapparatus for motor vehicles driven by internal combustion engines inwhich according to this invention exhaust gas is recirculated to the engine combustion chambers to lower exhaust gas emissions of NO, while vehicle driveability is substantially maintained. The Figure includes an EGR valve 10, of any one of the types well-known in the art, capable of controllably. recirculating exhaust gases, and carburetor 12 having a throttle valve 14 of the butterfly type. Carburetor venturi vacuum source means is provided by conduit 16 which tapsinto the venturi section 18 of carburetor l2 and thus senses the venturi vacuum. Engine manifold vacuum source means is provided by conduit 20 which taps into the carburetor below throttle valve 14 and thus senses engine manifold vacuum. Vacuumv reservoir means is provided by a vacuum contained 22 which is connected to conduit 20. via a check valve 24 such that container 22 is evacuated by the engine manifold vacuum. This vacuum is stored and maintained by container 22 and providedias an input vacuum via conduit 26, whichis connected at one end to container 22.

A vacuum amplifier, generally indicated at 28, is interconnected between carburetor 12 and vacuum reservoir container 22 by connection with venturi vacuum control conduit 16 and vacuum input conduit 26. The function of amplifier 28 is to provide a control output vacuum in conduit 30 for controlling the operation of able and substantially proportional to the relatively wealt venturi control signal vacuum.

One form of such an amplifier 28 is available commercially from RancoControl Division, 601 West Fifth Avenue, Columbus, Ohio 43201 and is described hereinbelow in detail.

the amplifier function as follows and can be considered to comprise a vacuum motor 32 and a vacuum regulator 34. Briefly, vacuum motor 32 includes a diaphragm 36 and operating means 38 which interconnects between diaphragm 36 and a diaphragm 40 of the vacuum regulator for operating diaphragm 40. The venturi vacuum control signal, operative in conduit 16 and the upper chamber 42 of amplifier 28, controls the portion of diaphragm 36 depending on the vacuum level of the venturi control vacuum and hence the position of diaphragm 40. Diaphragm 40 is designed to close off conduit 26 as shown and to lift from or open conduit 26 when the venturi vacuum control signal increases thereby increasing the output vacuum in conturi control vacuum decreases thereby closing EGR valve 10 as well. One arrangement for providing these functions will be discussed in detail in connection with FIG. 2. At this point it is sufficient to understand that the function of amplifier 28 is to receive the input vacuum of conduit 26 and to apply it to EGR valve 10 in accordance with the venturi vacuum control signal in conduit 16, thus in effect amplifying the venturi signal.

Thus, amplifier 28 provides a control means responsive to a vacuum control signal and operable to modulate, in accordance with the vacuum control signal, the operating vacuum provided to the EGR valve by the vacuum reservoir means 22.

Vacuum relief means is provided in accordance with this invention and in FIG. 1 takes the form of a vacuum operated diaphragm valve generally indicated at 50. Relief valve 50 includes a diaphragm 52 separating two chambers, a venturi vacuum chamber 54 and a manifold vacuum chamber 56, from each other. Venturi vacuum communicates with chamber 54 via conduit 58 which is a branch of conduit 16. Manifold vacuum is provided via conduit 65 which is branch of conduit 20. As shown'schematically diaphragm 52 seats on the end of conduit 60 to provide normal closure thereof. Chamber 56 is vented to manifold vacuum in conduit 65 by means of opening 62. It can readily be seen that when the venturi vacuum in chamber 54 reaches any given level which can be selected by the design of relief means 50, diaphragm 52 will lift from the end of conduit 60 thus venting container 22 via opening 62 to conduit 65 until it reaches the manifold vacuum level. Insofar as the present invention is concerned it is preferred that this valve 50 be designed to vent container 22 to the manifold vacuum level when the venturi vacuum exceeds the manifold vacuum level, for example, when the venturi vacuum is at about 2 inches of mercury (2" Hg) and the manifold vacuum level is at about l.72" of Hg or when venturi vacuum is within about 0.3" of the manifold vacuum level. In some instances it may be desirable to delay venting until the venturi vacuum exceeds manifold vacuum. This is also considered to be within the scope of this invention and such an effect may be readily achieved by using a spring biasing arrangement so that the manifold vacuum must be exceeded by a predetermined amount before relief is provided.

OPERATION The venturi vacuum control signal through conduit 16 is amplified by vacuum amplifier 28, preferably in a [:1 ratio from most motor vehicles, to a value which is basically limited by the reservoir source vacuum in container 22. The amplified output vacuum operates the vacuum controlled EGR valve as previously described. Reservoir container 22 also provides a vacuum source to amplifier 28 during accelerations when manifold vacuum is reduced. Check valve 24 is built into reservoir container 22 to trap high vacuum achieved at low speeds or decelerations. This arrangement provides a substantially constant input vacuum in conduit 26 for application through amplifier'28, modulation therein and transformation therefrom as a control vacuum for application to EGR valve 10. The dump valve means 50 vents the reservoir to the manifold vacuum level whenever venturi vacuum approaches or exceeds manifold vacuum, a wide-open throttle characteristic. This feature allows the EGR valve to close at WOT in order to achieve maximum engine power.

VACUUM AMPLIFIER-WITH INTEGRAL RELIEF FIG. 2 shows an integral vacuum amplifier designed to incorporate into one integrated structure the functions of vacuum reservoir 22, amplifier 28 and relief means 50, thus simplifying the overall arrangement, particularly insofar as plumbing is concerned. An amplifier of this type is presently offered by the Ranco Controls Division and is more completely described in their information bulletin No. 005-4-72 entitled EGR Vacuum Amplifier. The specific design of that particular amplifier is no part of the present invention nor is any claim made thereto.

In the integral amplifier, FIG. 2, parts similar to those shown in FIG. 1 are correspondingly numbered. The basic amplifier operates on the principal of a balance of force as created by the interaction of the input and output vacuum signals which are provided at 16 and 30, respectively, and the input thereof on the respective diaphragms 36 and 40. The ratio of the effective areas of these two diaphragms is fixed and equal to the designed degree of amplification. When the input signal is increased or decreased the output signal responds as the forces readjust themselves for new levels of equilibrium.

Vacuum regulation of the output at 30 is directly controlled by means of a hook-washer 62 and small diaphragm 64. As the force on hook washer 62 is increased, internal port 66 opens communicating output chamber 68 to the higher force vacuum provided by reservoir 22. As the vacuum in output chamber 68 rises so does the force acting on diaphragm 40 and opposing the force on the hook washer. When equilibrium is established the port recloses at the new higher vacuum level in the output chamber.

When the force on hook washer 62 is reduced, equilibrium is upset in the opposite direction and an external port 70 is formed between the upper edges of hook washer 62 and diaphragm 64 which vents output chamber 68 to atmosphere in atmospheric pressure chamber 72 which communicates through air vent 74 with atmosphere.

Relief valve 50 consists of a diaphragm separating the venturi signal provided at input conduit 16 from the manifold vacuum signal and reservoir 22. When venturi vacuum substantially equals or exceeds manifold vacuum (wide open throttle condition) the differential causes the relief valve diaphragm to lift venting reservoir 22 to input 20 thus dumping the output signal and causing closure of the EGR valve for maximum engine performance. The venturi signal at 16 also communicates at chamber 42 for operating venturi diaphragm 36.

It can be readily seen that the use of an integral amplifier arrangement as shown in FIG. 2 greatly simplifies the system and its installation since only three vacuum conduits are necessary: a manifold vacuum conduit, a venturi vacuum conduit and an output vacuum conduit.

Additionally, a thermal cut-off switch (not shown) located in the fresh air plenum may also be included if desired to open an air bleed at lower ambients, the

bleed level being interconnected with integral amplifier to the venturi vacuum. The air bleed reduces the venturi vacuum signal at low ambient temperatues, such as are present with a cold engine when first starting, and thus the output of the amplifier is reduced resulting in reduced recycle and improved driveability at low ambient temperatures.

Having described the invention, the exclusive rights which are claimed are defined as follows:

1. An exhaust gas recirculation control system for motor vehicles driven by internal combustion engines whereby exhaust gas is recirculated to the engine combustion chambers to lower exhaust gas emissions of NO, while vehicle driveability is substantially maintained, the system comprising:

a vacuum operated exhaust gas recirculation valve;

vacuum reservoir means for providing an operating control vacuum to the exhaust gas recirculating valve;

engine manifold vacuum source means operable by way of a check valve means to provide vacuum to the vacuum reservoir means duringengine operation;

control means responsive to a vacuum control signal and operable to modulate, in accordance with the vacuum control signal, the operating control vacuum provided to the exhaust gas recirculating valve by the vacuum reservoir means;

carburetor venturi vacuum source means operable to provide a carburetor venturi vacuum control signal to the control means during engine operation thereby effecting the operation of the control means and the modulation of the operating vacuum provided to the exhaust gas recirculating valve during engine operation, and

vacuum relief means operable to vent the vacuum reservoir means to engine manifold vacuum level whereupon the operating vacuum is no longer provided, the relief means including operating means controlled by and responsive to both venturi vacuum and manifold vacuum for opening the vacuum relief means and venting the vacuum reservoir means when the venturi vacuum achieves a predetermined relationship to the manifold vacuum level during which time exhaust gas recirculation is terminated due to closure of the exhaust gas recirculation valve.

2. The system according to claim 1 wherein the vacuum reservoir means includessaid check valve means for trapping vacuum achieved at low speeds and decelerations.

3. The system according to claim 1 wherein the relief means is connected between the vacuum reservoir means and the engine manifold vacuum source means.

4. The system according to claim 1 wherein the engine manifold vacuum source means comprises a conduit communicating at one end with the vacuum reservoir means and at another end it is adapted for connection to an internal combustion engine at a tap-in point suitable for interfacing with the engine manifold vacuum.

S, The system according to claim 1 wherein the control means is connected between the vacuum reservoir means and the exhaust gas recirculation valve.

6. The system according to claim 1 wherein the carburetor venturi vacuum source means comprises a conduit communicating at one end with control means and at another end it is adapted for connection to an internal combustion engine carburetor at a tap-in point for interfacing with the carburetor venturi vacuum.

7. The system according to claim 1 wherein the vacuum relief means is normally closed by the manifold vacuum and opened by the venturi vacuum when it approaches or exceeds the manifold vacuum.

8. An exhaust gas recirculation control system for motor vehicles driven by internal combustion engines whereby exhaust gas is recirculated to the engine combustion chambers to lower exhaust gas emissions of NO,, the system comprising:

engine power means operable to provide vacuum output meansadapted for connection to an exhaust gas recirculation valve; control means connected to the vacuum output means to control the vacuum thereof in accordance with a vacuum control signal;

vacuum reservoir means connected to the control means for providing a vacuum thereto to be controlled by the vacuum control signal;

vacuum input means adapted for connection to a source of input vacuum and communicating by copy of a check valve means with the vacuum reservoir means;

relief means communicating between the vacuum reservoir means and the vacuum input means for venting the former to the latter, the relief means being normally closed by the input vacuum, and

vacuum control means adapted for connection to a source of control vacuum and communicating with the control means for modulating the vacuum output provided thereby for the vacuum output means the relief means is also being connected to the source of control vacuum for opening it when the control vacuum achieves a predetermined relationship to the input vacuum, said source of control vacuum providing said vacuum control signal.

UNITED STATES PATENf l {OFFICE- CERTIFICATE OF CGRRECTION Patent No. 3 818 880 Dated June 25 1974 Inventods) Gary D. Dawson et a1 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 26, "contained" should read container line 54, "the" should read The same line 54, "function" shouldread functions Column 6, claim 8, line 37, delete f'copy" and insert way line 47, after "means" insert a comma; line 48, delete "is".

Signed and sealed this 5th day of November 1974.

(SEAL) ACCOBT. l

McCOY M. GIBSON JR. 0. MARSHALL DANN Arresting Officer Commissioner of Patents USCOMM-DC 603764 69 u.s. GOVERNMENT PRINTING OFFICE: 6 930 F ORM Po-fbso (10 69) 

1. An exhaust gas recirculation control system for motor vehicles driven by internal combustion engines whereby exhaust gas is recirculated to the engine combustion chambers to lower exhaust gas emissions of NOx while vehicle driveability is substantially maintained, the system comprising: a vacuum operated exhaust gas recirculation valve; vacuum reservoir means for providing an operating control vacuum to the exhaust gas recirculating valve; engine manifold vacuum source means operable by way of a check valve means to provide vacuum to the vacuum reservoir means during engine operation; control means responsive to a vacuum control signal and operable to modulate, in accordance with the vacuum control signal, the operating control vacuum provided to the exhaust gas recirculating valve by the vacuum reservoir means; carburetor venturi vacuum source means operable to provide a carburetor venturi vacuum control signal to the control means during engine operation thereby effecting the operation of the control means and the modulation of the operating vacuum provided to the exhaust gas recirculating valve during engine operation, and vacuum relief means operable to vent the vacuum reservoir means to engine manifold vacuum level whereupon the operating vacuum is no longer provided, the relief means including operating means controlled by and responsive to both venturi vacuum and manifold vacuum for opening the vacuum relief means and venting the vacuum reservoir means when the venturi vacuum achieves a predetermined relationship to the manifold vacuum level during which time exhaUst gas recirculation is terminated due to closure of the exhaust gas recirculation valve.
 2. The system according to claim 1 wherein the vacuum reservoir means includes said check valve means for trapping vacuum achieved at low speeds and decelerations.
 3. The system according to claim 1 wherein the relief means is connected between the vacuum reservoir means and the engine manifold vacuum source means.
 4. The system according to claim 1 wherein the engine manifold vacuum source means comprises a conduit communicating at one end with the vacuum reservoir means and at another end it is adapted for connection to an internal combustion engine at a tap-in point suitable for interfacing with the engine manifold vacuum.
 5. The system according to claim 1 wherein the control means is connected between the vacuum reservoir means and the exhaust gas recirculation valve.
 6. The system according to claim 1 wherein the carburetor venturi vacuum source means comprises a conduit communicating at one end with control means and at another end it is adapted for connection to an internal combustion engine carburetor at a tap-in point for interfacing with the carburetor venturi vacuum.
 7. The system according to claim 1 wherein the vacuum relief means is normally closed by the manifold vacuum and opened by the venturi vacuum when it approaches or exceeds the manifold vacuum.
 8. An exhaust gas recirculation control system for motor vehicles driven by internal combustion engines whereby exhaust gas is recirculated to the engine combustion chambers to lower exhaust gas emissions of NOx, the system comprising: engine power means operable to provide vacuum output means adapted for connection to an exhaust gas recirculation valve; control means connected to the vacuum output means to control the vacuum thereof in accordance with a vacuum control signal; vacuum reservoir means connected to the control means for providing a vacuum thereto to be controlled by the vacuum control signal; vacuum input means adapted for connection to a source of input vacuum and communicating by copy of a check valve means with the vacuum reservoir means; relief means communicating between the vacuum reservoir means and the vacuum input means for venting the former to the latter, the relief means being normally closed by the input vacuum, and vacuum control means adapted for connection to a source of control vacuum and communicating with the control means for modulating the vacuum output provided thereby for the vacuum output means the relief means is also being connected to the source of control vacuum for opening it when the control vacuum achieves a predetermined relationship to the input vacuum, said source of control vacuum providing said vacuum control signal. 